You may have noticed that there are two versions of the 3-pin switching regulator for sale, the PSU1 and PSU2. Both Regulators are available in 5V and 3.3V versions and I'm often asked what the difference is between the two regulators. The PSU1 design is rated at 40V input and is more accurate than the PSU2 design. The PSU2 design is only rated at 17V on the input and is NOT suitable for use in an automobile because it does not survive the spikes present on the '12V' in a car. The PSU1 works well in cars and trucks.

The other major difference is the switching frequency; The PSU1 switches at 300kHz and the PSU2 at 3MHz. The larger inductor on the PSU1 has a bigger leakage field (it is not as well shielded) as the tiny inductor on the PSU2 and may cause more noise coupling to nearby circuits.